Binary and Ternary Blended Portland Cements Containing Different Types of Rice Husk Ash.

Rice husk ash (RHA) is agricultural waste with high silica content that has exhibited proven technical feasibility as a pozzolanic material since the 1970s. Notwithstanding, its use in mortars and concrete is limited by the standards currently utilized in some countries where RHA production is high and the aforementioned pozzolanic material is not standardized. This is the case in Spain, one of the main rice producers in Europe.

Influence of Accelerators on Cement Mortars Using Fluid Catalytic Cracking Catalyst Residue (FCC): Enhanced Mechanical Properties at Early Curing Ages.

Supplementary cementitious materials (SCMs) have been used in the construction industry to mainly reduce the greenhouse gas emissions associated with Portland cement. Of SCMs, the petrochemical industry waste known as fluid catalytic cracking catalyst residue (FCC) is recognized for its high reactivity. Nevertheless, the binders produced using SCMs usually present low mechanical strength at early curing ages.

Study of the Pozzolanic Reactivity of Sugar Cane Straw Ashes (SCSA) Burned under Controlled Conditions.

The aims of this work were to evaluate the reactivity of sugarcane straw ashes (SCSA) burned under controlled conditions and to analyze their reactivity in blended cement and hydrated lime pastes by thermogravimetric analysis (TG) and calorimetry. Four different ashes were produced, and burned at 600 °C, 700 °C, 800 °C and 900 °C (SCSA600, SCSA700, SCSA800 and SCSA900, respectively). These ashes were characterized by X-ray fluorescence spectroscopy, X-ray diffractometry, particle size distribution by laser diffraction and specific area surfaces to assess their potential interest in the partial replacement of inorganic binders (Portland cement (OPC) and hydrated lime).

Evaluation of Thermochemical Treatments for Rice Husk Ash Valorisation as a Source of Silica in Preparing Geopolymers.

The use of geopolymers has revolutionized research in the field of construction. Although their carbon footprint is often lower than that of traditional mortars with Portland cement, activators such as sodium silicate have a high environmental impact in the manufacturing of materials. Employing alternative alkali sources to produce geopolymers is necessary to obtain materials with a lower carbon footprint.

Impedance Spectroscopy as a Methodology to Evaluate the Reactivity of Metakaolin Based Geopolymers.

The aim of this study was to use the electrical impedance spectroscopy technique (IS) to carry out a systematic study on the mechanism of metakaolin geopolymerization for up to 7 curing days. The study was developed on two batches of metakaolin (MK), and their reaction processes were compared. Interpretative fundamental elements were developed based on the effective electrical conductivity curves regarding the metakaolin geopolymerization.

Reusing Construction and Demolition Waste to Prepare Alkali-Activated Cement.

Large amounts of waste are derived not only from construction processes, but also the demolition of existing buildings. Such waste occupies large volumes in landfills, which makes its final disposal difficult and expensive. Reusing this waste type is generally limited to being employed as filler material or recycled aggregate in concrete, which limits its valorisation.

Hybrid Lime-Pozzolan Geopolymer Systems: Microstructural, Mechanical and Durability Studies.

This work studies the possibility of using geopolymer materials to enhance the mechanical and durability properties of hydrated lime-pozzolan mixtures, which gave rise to the so-called "hybrid systems". Two different waste types were used as pozzolan in the lime-pozzolan system: rice husk ash (RHA) and spent fluid catalytic cracking (FCC). The geopolymer fabricated with FCC was activated with commercial reagents (NaOH and NaSiO), and also with alternative sources of silica to obtain a lower carbon footprint in these mixtures.

Reuse of Industrial and Agricultural Waste in the Fabrication of Geopolymeric Binders: Mechanical and Microstructural Behavior.

Resource recovery from waste is one of the most important ways to implement the so-called circular economy, and the use of alkali activated materials can become an alternative for traditional PC-based materials. These types of materials are based on waste resources involving a lower carbon footprint and present similar or high properties and good durability compared to that Portland cement (PC). This research work proposes using new waste generated in different types of industries.

Concrete for Precast Blocks: Binary and Ternary Combination of Sewage Sludge Ash with Diverse Mineral Residue.

This paper proposes binary and ternary combinations of sewage sludge ash (SSA) with fly ash (FA), marble dust (MD) and rice husk ash (RHA) as partial replacements of Portland cement in concretes with a similar dosage to that used in precast blocks, with very dry consistency. Several physical-mechanical tests were carried out on concrete specimens with curing ages of 28 and 90 days: density, water absorption, capillary water absorption, ultrasonic pulse velocity and compressive strength. The combinations of residues significantly improve the properties of the cementitious systems: 30% replacement of Portland cement provides strength values similar to the reference sample, showing the synergetic effects of the combination of the mineral additions.

Comparative Study of Coupling Techniques in Lamb Wave Testing of Metallic and Cementitious Plates.

Lamb waves have emerged as a valuable tool to examine long plate-like structures in a faster way compared to conventional bulk wave techniques, which make them attractive in non-destructive testing. However, they present a multimodal and dispersive nature, which hinders signal identification. Oblique incidence is one of the most known methods to generate and receive Lamb waves and it is applied in different experimental arrangements with different types of sensors.

Microscopic Chemical Characterization and Reactivity in Cementing Systems of Elephant Grass Leaf Ashes.

Many agrowastes are being used for energy production by combustion in power plants. This process generates huge amounts of ash, which has a potential pozzolanic activity for blending with Portland cement or hydrated lime. In this paper, the ash obtained from elephant grass (Pennisetum purpureum Schum var.

Use of ancient copper slags in Portland cement and alkali activated cement matrices.

Some Chilean copper slag dumps from the nineteenth century still remain, without a proposed use that encourages recycling and reduces environmental impact. In this paper, the copper slag abandoned in landfills is proposed as a new building material. The slags studied were taken from Playa Negra and Púquios dumps, both located in the region of Atacama in northern Chile.

Microscopy Characterization of Silica-Rich Agrowastes to be used in Cement Binders: Bamboo and Sugarcane Leaves.

Agrowastes are produced worldwide in huge quantities and they contain interesting elements for producing inorganic cementing binders, especially silicon. Conversion of agrowastes into ash is an interesting way of yielding raw material used in the manufacture of low-CO2 binders. Silica-rich ashes are preferred for preparing inorganic binders.

Assessment of Pozzolanic Activity Using Methods Based on the Measurement of Electrical Conductivity of Suspensions of Portland Cement and Pozzolan.

The use of methods based on measuring electrical conductivity to assess pozzolanic activity has recently been used primarily in aqueous suspensions of pozzolan: calcium hydroxide. However, the use of similar methods in suspensions of cement with pozzolans has not been widely studied. This paper proposes a new method for rapid assessment of the pozzolanic activity of mineral admixtures in aqueous cement suspensions.

Assessment of the Pozzolanic Activity of a Spent Catalyst by Conductivity Measurement of Aqueous Suspensions with Calcium Hydroxide.

The pozzolanic activity of the spent catalyst produced by fluid catalytic cracking (FCC) has been studied by various methods in recent years. However, no quick and easy method has been reported for this activity based on the associated studies. In this work, the pozzolanic activity of a spent catalyst was investigated by measuring its electrical conductivity in aqueous suspensions of pozzolan/calcium hydroxide.

Use of Slag/Sugar Cane Bagasse Ash (SCBA) Blends in the Production of Alkali-Activated Materials.

Blast furnace slag (BFS)/sugar cane bagasse ash (SCBA) blends were assessed for the production of alkali-activated pastes and mortars. SCBA was collected from a lagoon in which wastes from a sugar cane industry were poured. After previous dry and grinding processes, SCBA was chemically characterized: it had a large percentage of organic matter ( 25%).

Increase of the reactivity of densified silica fume by sonication treatment.

Five silica fumes from different manufacturers were subjected to ultrasonic treatment in order to decrease particle agglomeration and improve particle dispersion. The effectiveness of the sonication was observed as a reduction in particle size distribution of sonicated silica fume (SSF) compared to non-sonicated silica fume. SSF was added to Portland cement, and then the hydrated paste was analysed by thermogravimetric analyses (TGA/DTG) and scanning electron microscopy (SEM/EDX).